Routine traffic stops by police officers generally require the officer to get out of the police vehicle. Such stops also require the officer to walk to, and stand next to the driver of the vehicle that is pulled over. This is usually on the shoulder or side of a highway or street. The officer then talks to, and can see the driver of the pulled over vehicle, including the driver's facial expressions. The officer can exchange documents and communicate with the driver.
A problem with this practice is that it leaves the officer unprotected if one of the vehicle's occupants wants to engage in a hostile act. Moreover, the officer typically has to stand close to the side of the road. This leaves the officer in an unprotected position in the event traffic comes too close.
Other conventional methods for police officers to communicate with drivers include use of a loud speaker. But the use of a loud speaker is only practical for one-way communication from a distance, and therefore not commonly used for most traffic stops. Use of the loud speaker does not allow the officer to obtain documents from the driver, such as a driver's license, and proof of insurance.